The invention relates generally to sound field modeling and creation of a sound event based on a modeled sound field, and more particularly to a method and apparatus for capturing a sound field with a plurality of sound capture devices located on an enclosing surface, modeling and storing the sound field and subsequently creating a sound event based on the stored information.
Existing sound recording systems typically use two or three microphones to capture sound events produced by a sound source, e.g., a musical instrument. The captured sounds can be stored and subsequently played back. However, various drawbacks exist with these types of systems. These drawbacks include the inability to capture accurately three dimensional information concerning the sound and spatial variations within the sound (including full spectrum xe2x80x9cdirectivity patternsxe2x80x9d). This leads to an inability to accurately produce or reproduce sound based on the original sound event. A directivity pattern is the resultant sound field radiated by a sound source (or distribution of sound sources) as a function of frequency and observation position around the source (or source distribution). The possible variations in pressure amplitude and phase as the observation position is changed are due to the fact that different field values can result from the superposition of the contributions from all elementary sound sources at the field points. This is correspondingly due to the relative propagation distances to the observation location from each elementary source location, the wavelengths or frequencies of oscillation, and the relative amplitudes and phases of these elementary sources. It is the principle of superposition that gives rise to the radiation patterns characteristics of various vibrating bodies or source distributions. Since existing recording systems do not capture this 3-D information, this leads to an inability to accurately model, produce or reproduce 3-D sound radiation based on the original sound event.
On the playback side, prior systems typically use xe2x80x9cImplosion Typexe2x80x9d (IMT) sound fields. That is, they use two or more directional channels to create a xe2x80x9cperimeter effectxe2x80x9d sound field. The basic IMT method is xe2x80x9cstereo,xe2x80x9d where a left and a right channel are used to attempt to create a spatial separation of sounds. More advanced IMT methods include surround sound technologies, some providing as many as five directional channels (left, center, right, rear left, rear right), which creates a more engulfing sound field than stereo. However, both are considered perimeter systems and fail to fully recreate original sounds. Perimeter systems typically depend on the listener being in a stationary position for maximum effect. Implosion techniques are not well suited for reproducing sounds that are essentially a point source, such as stationary sound sources (e.g., musical instruments, human voice, animal voice, etc.) that radiate sound in all or many directions.
Other drawbacks and disadvantages of the prior art also exist.
An object of the present invention is to overcome these and other drawbacks of the prior art.
Another object of the present invention is to provide a system and method for capturing a sound field, which is produced by a sound source over an enclosing surface (e.g., approximately a 360xc2x0 spherical surface), and modeling the sound field based on predetermined parameters (e.g., the pressure and directivity of the sound field over the enclosing space over time), and storing the modeled sound field to enable the subsequent creation of a sound event that is substantially the same as, or a purposefully modified version of, the modeled sound field.
Another object of the present invention is to model the sound from a sound source by detecting its sound field over an enclosing surface as the sound radiates outwardly from the sound source, and to create a sound event based on the modeled sound field, where the created sound event is produced using an array of loud speakers configured to produce an xe2x80x9cexplosionxe2x80x9d type acoustical radiation. Preferably, loudspeaker clusters are in a 360xc2x0 (or some portion thereof) cluster of adjacent loudspeaker panels, each panel comprising one or more loudspeakers facing outward from a common point of the cluster. Preferably, the cluster is configured in accordance with the transducer configuration used during the capture process and/or the shape of the sound source.
According to one object of the invention, an explosion type acoustical radiation is used to create a sound event that is more similar to naturally produced sounds as compared with xe2x80x9cimplosionxe2x80x9d type acoustical radiation. Natural sounds tend to originate from a point in space and then radiate up to 360xc2x0 from that point.
According to one aspect of the invention, acoustical data from a sound source is captured by a 360xc2x0 (or some portion thereof) array of transducers to capture and model the sound field produced by the sound source. If a given soundfield is comprised of a plurality of sound sources, it is preferable that each individual sound source be captured and modeled separately.
A playback system comprising an array of loudspeakers or loudspeaker systems recreates the original sound field. Preferably, the loudspeakers are configured to project sound outwardly from a spherical (or other shaped) cluster. Preferably, the soundfield from each individual sound source is played back by an independent loudspeaker cluster radiating sound in 360xc2x0 (or some portion thereof). Each of the plurality of loudspeaker clusters, representing one of the plurality of original sound sources, can be played back simultaneously according to the specifications of the original soundfields produced by the original sound sources. Using this method, a composite soundfield becomes the sum of the individual sound sources within the soundfield.
To create a near perfect representation of the soundfield, each of the plurality of loudspeaker clusters representing each of the plurality of original sound sources should be located in accordance with the relative location of the plurality of original sound sources. Although this is a preferred method for EXT reproduction, other approaches may be used. For example, a composite soundfield with a plurality of sound sources can be captured by a single capture apparatus (360xc2x0 spherical array of transducers or other geometric configuration encompassing the entire composite soundfield) and played back via a single EXT loudspeaker cluster (360xc2x0 or any desired variation). However, when a plurality of sound sources in a given soundfield are captured together and played back together (sharing an EXT loudspeaker cluster), the ability to individually control each of the independent sound sources within the soundfield is restricted. Grouping sound sources together also inhibits the ability to precisely xe2x80x9clocatexe2x80x9d the position of each individual sound source in accordance with the relative position of the original sound sources. However, there are circumstances which are favorable to grouping sound sources together. For instance, during a musical production with many musical instruments involved (i.e., full orchestra). In this case it would be desirable, but not necessary, to group sound sources together based on some common characteristic (e.g., strings, woodwinds, horns, keyboards, percussion, etc.).
These and other objects of the invention are accomplished according to one embodiment of the present invention by defining an enclosing surface (spherical or other geometric configuration) around one or more sound sources, generating a sound field from the sound source, capturing predetermined parameters of the generated sound field by using an array of transducers spaced at predetermined locations over the enclosing surface, modeling the sound field based on the captured parameters and the known location of the transducers and storing the modeled sound field. Subsequently, the stored sound field can be used selectively to create sound events based on the modeled sound field. According to one embodiment, the created sound event can be substantially the same as the modeled sound event. According to another embodiment, one or more parameters of the modeled sound event may be selectively modified. Preferably, the created sound event is generated by using an explosion type loudspeaker configuration. Each of the loudspeakers may be independently driven to reproduce the overall soundfield on the enclosing surface.
Other embodiments, features and objects of the invention will be readily apparent in view of the detailed description of the invention presented below.